Sliding contacts for push button switches



I United States Patent Willis Edwin Spaeth;

George Peter Piotrowski, Milwaukee; Edward Marion Sadowski, Brooklleld, Wisconsin April 4, 1 969 Dec. 8, 1970 Globe-Union Inc.

Milwaukee, Wisconsin a corporation of Delaware 72] inventors Appl. No. Filed Patented Assignee SLIDING CONTACTS FOR PUSH BUTTON SWITCHES 7 Claims, 9 Drawing Figs.

Us. Cl. 200116, 200/166, norms/0o Field of Search 200/ i 6, 166(8), 8

References Cited UNITED STATES PATENTS 3,270,l49 8/l966 OShea et al 3,352,980 I 1/1967 Du Temple De Roughlemont et ai.

, 200/16 3,37 l ,168 2/1968 Milner 200/l 6 3,399,282 8/l968 Nagashima et al ZOO/16X 3,461,252 8/1969 Vananzi 200/16 Primary Examiner-Robert K. Schaefer Assistant Examiner-U. R. Scott Attorneys-John Phillip Ryan, Glenn A. Buse, Donald D.

Denton and David T. Terry ABSTRACT: A pushbutton switch having a stator housing, in which fixed contacts are mounted in spaced relationship, and a slider bar, carrying sliding contacts arranged to bridge adjacent fixed contacts, slidably mounted in the housing. The

sliding contacts are arranged in recesses in the slider bar and biasing means disposed in the recesses provide at least three independent sources of force to urge the conductive portion of the sliding contacts into engagement with the fixed contacts to insure positive electrical contact therebetween during a changeover of switch positions resulting from movement of the slider bar.

' switches. 2. Description of the Prior Art BACKGROUND OF THE INVENTION 1. Field ofthe Invention v This invention relates to'electrical switches and more particularly to sliding contact-arrangements for pushbutton One particular type of known pushbutton switches employs a housing or stator block supporting a plurality of fixed contact terminals, which are connected to the electrical circuit being controlled by the switch, and a selector or slider bar slidably disposed in the stator block which carries sliding contacts adapted to bridge and, connect adjacent fixed contacts. As the slider bar is actuated'by a pushbutton mechanism, it changes positions and the desired switching function is performed as selected fixed contacts are bridged by the sliding contacts. When switches of this type are used in certain audio circuits, such as in tape recorders or high fidelity musical equipment, there is frequently an undesired audible pop as the sliding contacts make the changeover from one circuit to another.-The problem can be overcome by making the sliding contacts long enough to bridge several adjacent fixed contacts as the slider bar is being moved to the actuated position. By this means, second circuit is completed before the first circuit is broken thereby eliminating the pop."

In order to minimize the noise during switching, it is necessary to'maintain good engagement between the sliding and fixed contacts. Typical prior art switches employ sliding contacts shaped in the form of a lot hook which are held in a recess provided in the slider bar. Such sliding contacts tend to rock during the changeoverbetween fixed contacts thereby causing a loss'of engagement with the fixed contacts and a resultant noisy operation-Also, sliding contacts of this design are not readily adaptable to bridging several fixed contacts.

SUMMARY OF THE INVENTION Accordingly, an object of this invention is to provide a pushbutton switch wherein means is provided for maintaining positive electrical contact between the sliding and fixed contacts during the switching operation. Another object of this invention is to provide an improved pushbutton switch, adaptable for use in audio circuits,'which is capable of changing switch positions with substantially no noise generation.

According to this invention,'the sliding contacts are formed from a' strip of resilient," conductive material and biasing means are provided for applying at least three independent sources of force urging the conductive material into engagement with the fixed contacts as the slider bar is actuated, thereby insuring maintenance of positive contact between the sliding and fixed contacts throughout the switching operation. In one embodiment the means. providing the independent sources of biasing force comprise arcuate spring sections formed as an integral. portion of the conducting strip. In another embodiment resilient backup means making localized contact with the strip of conducting material provide the independent sources of biasing force.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of an exemplary switching module to which this invention is adaptable.

FIG. 2 is a cross-sectional view of aswitching module showing the relationship of the sliding and fixed contacts.

FIG. 3 is a perspective, exploded view of a portion of a slider bar carrying sliding contacts constructed in accordance with one embodiment of this invention.

FIGS. 4, 5 and 6 are sectioned elevation views taken along the plane of line A-A in FIG. 2 showing the combined action, in three different positions, of the sliding contacts of one embodiment of this invention and the fixed contacts.

FIGS. 7, 8 and 9 are partial, broken-away, elevation views of a switching module embodying modified forms of the sliding contacts shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The switch arrangement embodying this invention includes a switching module 10 comprised of a hollow stator block 12, a slider bar 14, a plurality of fixed contact terminals 16, sliding contacts 18, return spring 20, an'd pushbutton 22.

In accordance with one embodiment of this invention, as illustrated in FIGS. 3-6, sliding contacts 18 are an integral unit having a flat contact surface 24 and a plurality of arcuate spring portions 26 constructed from a resilient, conductive material, preferably a silver plated elastic metal. Contact surface 24 and spring portions 26 can be formed from a single strip of conductive material as shown or spring portions 26 can be separate parts attached to a flat strip in any conventional manner.

Spring portions 26 are dimensioned so that, when sliding contacts 18 are fitted'into recess 28 of slider bar 14 and switch module 10 is assembled, the spring portions are in slight compression thereby urging contact surface 24 into engagement with fixed contacts 16. These spring portions provide independent su sources of force in a direction generally normal to the contact surface 24 thereby insuring positive contact between contact surface 24 and fixed contacts 16 as the position of slider bar 14 is changed.

FIGS. 46 show the relationship of the sliding contacts 18 and fixed contact 16 as slider bar 14 is moved to the left to make a changeover in switching positions. In order to simplify the description and drawing, the operation of only one of the pair of illustrated sliding contacts will be described and given reference numerals. As slider bar 14 is moved from one switching position (FIG. 4) where contact surface 24 bridges fixed contact 160 and 16b to another switching position (FIG. 6) where contact surface 24 bridges fixed contact 16b and 16c, contact surface 24-is urged into contact with fixed contact 16c by spring section 26c before breaking contact with fixed contact 16a (FIG. 5). Hence, an audio circuit connected to fixed contacts 161; and 160, is completed before the circuit connected to contacts 16a and 16b is opened thereby preventing a pop." As slider bar 14 is moved to the left, a reverse of above-described action will occur, i.e., contact surface 24 is urged into contact with fixed contact 16a by spring section 26a before breaking contact with fixed contact 16c.

The force applied by spring sections 26 is applied to contact surface 24 at areas generally coincident with the respective fixed contact 16 when the slider bar 14 is moved to different switching positions so that contact surface 24 is bridging two or three adjacent fixed contacts. The independent sources of biasing force provided by spring sections 26a, 26b and 26c insure that positive contact is'maintained between contact surface 24 and fixed contact 16a, 16b and 16c during the switchover operation. The provision of these independent sources of force, coupled with a resilient nature of contact surface 24, minimizes friction between the fixed contacts 16 and contact surface 24 as slider bar 14 is actuated. It should be understood that this same arrangement can be used for a greater number of changeover switching positions than that illustrated.

FIG. 7 illustrates an alternate embodiment of this invention where the sliding contact 30is formed from a rectilinear strip of resilient, conductive material having a flat contact surface 32 and a pair of opposed extremities 34 and 36 configured to abut walls 38 and 40, respectively, of recess 28 in slider bar 14 Backup member 42 is preferably freely inserted into recess 28; however, it can be attached to contact surface member if desired. Backup member 42 is dimensioned so that, when the sliding contacts 30 are fitted into recess 28 of slider bar 14 and switch module 10 is assembled, it is slightly compressed thereby urging contact surface 32into engagement with fixed contacts 16.

, FIG. 8 illustrates an alternate embodiment of this invention where the sliding contact 44 is formed from a rectilinear strip of resilient conductive material having a flat contact surface 46and a pair of opposedextremities 48 and 50 configured to abut walls 52 and 54, respectively, of recess 56 in slider bar 58. In this embodiment, the independent biasing source of biasing force is provided by a backup member 60, formed from an elastic, insulating material, such as neoprene rubber, which has a plurality of lateral extensions 62. When assembled into s switch module 10, extensions 62 are slightly compressed so'as to urge contact surface 46 into engagement with fixed contacts 16. Protuberance 64 and 66 and recess 56 of slider bar 56 are configured so that backup member 60 is in longitudinal compression when inserted into recess 56.

FiG. 9 illustrates another alternate embodiment of this invention where the sliding contact 68 is formed from a rectilinear strip of resilient conducting material having a flat contact surface 70 and a pair of opposed extremities 72. and 74 configured to abut walls 76 and 78, respectively, of recess 80 in slider bar 82. In this embodiment, the independent sources of biasing force is provided by elongated members 84, formed from an elastic, insulating material, such as neoprene rubber, carried in lateral recesses 86 provided in slider bar 82.

Although the various embodiments of this invention have been illustrated and described with a slider bar carrying one pair of sliding contacts, it should be understood that the sled slider bar can carry any number of sliding contacts.

As will be readily apparent to those skilled in the art upon reading the above description of this invention, various modifications can be made thereto without departing from the spirit and scope thereof.

We claim:

1'. A pushbutton switch comprising a stator housing; a plurality of spaced fixed contacts, adaptable for connection to external circuits, mounted in said housing; a slider bar having at least one recess slidably mounted in said housing for reciprocating movement; a sliding contact element, having a conductive portion with a substantially flat surface adapted to wipe over said fixed contacts and bridge adjacent fixed contacts, disposed in said recess; said conductive portion dimensioned so that a circuit connected to a first adjacent pair of fixed contacts is completed therethrough before a circuit connected to a second adjacent pair of fixed contacts is broken during a changeover effected by the movement of said slider bar; and biasing means disposed in said recess for applying at least three independent sources of localized force urging said conductive portion into engagement with said fixed contacts to insure positive contact therebetween during the changeover.

2. The switch according to claim 1 wherein said biasing means comprises arcuate spring sections.

3. The switch according to claim 2 wherein said spring sections are integral with said conductive portion.

4. The switch according to claim 3 wherein said conductive portion and said arcuate spring sections are formed from a single strip of conductive material.

5. The switch according to claim 1 wherein said biasing means comprises a corrugated, flexible member arranged to make at least three points of contact with said conductive portions and disposed in slight compression so as to provide said localized forces.

6. The switch according to claim 1 wherein said biasing means comprises a resilient member having at least three lateral extensions contacting said conductive portion and disposed in slight compression so as to provide said localized forces.

7. The switch according to claim 1 wherein said slider bar further includes a plurality of lateral recesses and said biasing means comprises elongated resilient members disposed in said lateral recesses, said elongated resilient members contacting said conductive portion in slight compression so as to provide said localized forces. 

